Posts Tagged ‘Placebo’

Suggestible You 6

March 22, 2017

“Suggestible You” is the title of a book by Erik Vance.  The subtitle is “The Curious Science of Your Brain’s Ability to Deceive, Transform, and Heal.  This post is about the placebo response and related phenomena.   This is the sixth post on this book.

This post is on nocebos.  Remember that placebo is Latin for “I shall please.”  Nocebo means “I shall harm.”  So nocebos can be thought of as negative placebos.

In 1886 a physician named John Mackenzie was treating a woman with a serious case of hay fever and asthma.  For a variety of reasons, he was not convinced that the patient’s condition was fully authentic.  For her next visit he place a rose in his office.  As soon as she sat it she had powerful allergic reaction that brought on an asthma attack.  The flower was artificial and served as the nocebo.

Cholecystokinin (CCK) is a key messenger in activating intestinal functions, including digestion and the release of gastric acid and bile.  It also plays a role in making you feel full after a good meal.  But if you inject CCK into someone, it causes anxiety and nausea and can induce panic attacks.  It also seems to increase pain by lessening the impact of internal opioids.  Fabrizio Benedetti set up an experiment with patients recovering from  minor surgery in which he gave them a drug and told them it would make their pain worse when it was actually just saline.  The patients did report more pain with the saltwater injection.  Then Benedetti blocked their brains’  CCK release with another drug.  Now the patients felt better when the CCK was blocked.  Vance wrote,”What opioids are for placebos is what CCK is for nocebos; a mechanism giving expectation power in the body.  And whereas blocking opioids killed the placebo response and made patients feel worse, blocking CCK actually supercharged pain relief by allow the brain’s internal pharmacy to run wild.”

Nocebo effects are much easier to create than placebo effects.  Negative expectations can be stronger than positive expectations.  Vance note that nocebos and placebos in the brain take two different routes.  They look similar, go to similar places, share some of the same highways, but still are totally different routes, and nocebos take all the best shortcuts.  This does make  sense, as the aversion to pain is fundamental not just to being human, but also to being alive.  Colloca notes that although the nocebo affects the same reward/expectation regions in the brain, it also includes one more that placebos do not:  fear.  The hippocampus plays a key role in the storage of memories and it also plays a key role in fear conditioning anxiety.  Brain imaging indicates that while the hippocampus is mostly absent from placebo effects, it lights up during the experience of nocebos.

Fear is at the heart of nocebos, and fear is a powerful emotion.  Fear headlines in the news elicit much stronger responses that do pleasant ones.  In 2014, even before anyone had died of Ebola in the United States, 25% of Americans were worried they or their families could contract it.  Thousands of people visited doctors claiming they had signs of the virus, and 650 of those people had symptoms serious enough for their cases to be passed on to federal officials.  As it turned out, only four people in the United States had the disease:  a visitor who got it in Liberia, two nurses who had treated him, and a doctor who had been working in an Ebola.

So we need to be careful to not let our fears get out of hand.  And let us hope that doctors make more use of nocebos in treating pain.

Suggestible You 5

March 21, 2017

“Suggestible You” is the title of a book by Erik Vance.  The subtitle is “The Curious Science of Your Brain’s Ability to Deceive, Transform, and Heal.  This book is about the placebo response and related phenomena.   This is the fifth post on this book.

Vance describes the story of a man diagnosed ten years ago being severely debilitated in late stage Parkinson.  He volunteered for an experiment in which the medication was directly injected into a critical part of the brain.  To control for the placebo effect, these experiments require sham surgery that copies everything about the surgery except for the critical drug injected into the brain.  The study involved 51 participants.  Twenty-four people got the real surgery and 27 got the sham surgery.  The drug proved to be a failure.  However, the participant of interest did show a remarkable recovery.  However, he was one of those who had received sham surgery.

This dramatic example makes the point that there are large individual differences in the response to placebos.  Kathryn Hall of Harvard University was interested in studying possible genetic bases for this enhanced responsively.  She discovered the COMT gene.  The COMT genes codes for an enzyme in the brain, also called COMT, or catechol-O-methyltransferase.  Vance writes that this is one of the best-studied brain pathways in the world, and may be the most fascinating link he has discovered as a science writer.

Here’s how it works.  Dopamine has enormous power and is important for body movement and good moods.  However, it is possible to have too much of a good thing.  A mechanism is need to sweep up the bits we don’t need—the extra dopamine molecules floating around our skull that aren’t doing anything useful.  COMT gets rid of the excess dopamine molecules.  COMT is an extremely long and complicated enzyyme.  Fortunately, it is one within its machinery that defines how well it works.  Depending upon an individual’s genetics there are two types of this crucial portion of the enzyme:  valine (val) or methionine (met).  If one’s brain has val in that one spot, the enzyme performs its job of removing excess dopamine.  However, if the enzyme has met in that one spot, it is much less effective.  The brain is left with lots of excessive dopamine.

Remember that each trait in the body is a combination from each of the parents.  COMT works in a similar manner.  So we have val/met, but also val/vals and met/mets.  So 25% of the population are val/vals,and 25% are met/mets, 50% of the population are val/mets.

Hall conducted an experiment pairing COMT genes with placebos.  She enrolled 262 patients with irritable bowel syndrome (IBS) into an experimental treatment involving acupuncture.  She selected patients with either moderate or severe cases of IBS and then divided them into three groups. One group, the true control group, was put on a waiting list and given nothing.  The other two groups were told that they would get acupuncture, but they were unknowingly given fake acupuncture.  Half of the participants got treatment from a comforting, caring acupuncturist while the others got treatment from a cold, uncaring acupuncturist.

Here are the results.  People on the waiting list stayed the same regardless of their genes.

Met/mets with the uncaring acupuncturist  did better than the val/vals, but just barely.

Val/vals with the caring acupuncturist did about as well as the val/vals with the uncaring acupuncturist and all the people on the waiting list. In short, no placebo effect.

The val/mets who got the caring acupuncturist did about five times better.

The results of the met/mets who got the caring doctor went through the roof.

Clearly the kind words  meant something totally different to one genotype than it did with the others.  Hall had divided the placebo responders into measurable groups.Met/mets—those people who were born with lazy enzymes and a little too much dopamine in their responses were more prone to placebo responses.

Although the COMT gene plays a large role in the creation of the COMT enzyme, it’s not the only gene that does so.  Other genes help build the enzyme that can boost or cripple its performance, as well as all the other genes in you body that affect dopamine.    COMT also goes after epinephrine and norepinephrine, neurotransmitters that are key to regulating adrenaline, cardiac, function, and our response to stress.

So, in summary, the interactions are complex.  But different factors that contribute to the immune response are being identified.  Genes, the administrator of the placebo, and our fellow human beings are factors.

Suggestible You 4

March 20, 2017

“Suggestible You” is the title of a book by Erik Vance.  The subtitle is “The Curious Science of Your Brain’s Ability to Deceive, Transform, and Heal.  This book is about the placebo response and related phenomena.   This is the fourth post on this book.

An important question is whether there is a way to enhance the placebo effect, or even make it permanent.  In 2015 Karin Jensen, a placebo researcher at Harvard,  published an experiment that showed how our brains can self-medicate even when we are not paying attention.  She set up a two phase experiment in which subjects wore a painful heat pad that flared up whenever they saw a picture of a certain face and died down when they saw another, similar face.  The brain learns that one face is bad and the other face is good.

In the next phase, after the relationship had been ingrained in the participant, she turned the heat to somewhere in the middle.  This time she showed the picture for only a fraction of a second, so the participants could barely see the face.  The subconscious mind could spot the difference, but the conscious mind could not.  Nevertheless the participants continued to feel pain with the bad face, and less pain with the good face, even when they could not consciously distinguish the faces.  With enough practice, people can unconsciously trigger the placebo effect with the flash of one face, even though their conscious mind has no idea its happening.

The placebo effect can also be altered by peer pressure.  One of Wager’s students, Leonie Koban, set up an experiment in which people  rated various levels of heat pain applied to their arms by a metal pad.  After gauging each person’s pain threshold, she asked them to rate how much pain they expected to feel before she applied it, but with one additional crucial element.  They would also be able to see how other people had rated the same pain.  These previous reports of pain were totally made up.  Still, people who felt a strong pain rated it lower if that’s what they thought others had done.  And people who were told others had felt a lot of pain rated the pain highly even if it was mild.  This peer pressure placebo effect was twice as strong as the normal placebo effect!  As a check, Koban recorded their skin conductance, which is a physiological response to pain.  On the basis of skin conductance it was impossible to differentiate from a genuine experience.

It seems that people are programmed with a preexisting need to go with the herd.  People quickly tapped into a more powerful placebo response than if they had spent hours conditioning themselves.  So someone else’s opinion is not only powerful, but it can be more powerful than your experience and even more powerful than repeated conditioning.  So we are hardwired to follow other people’s opinions.

Vance suggests that there might be some biochemistry involved in this interaction.  Luana did an experiment similar to the one reported in Suggestible You 2 in which a green screen induced a placebo effect.  The participants in this new experiment were given a dose of vasopressin before the green screen experiment. In yet another experiment the participants were given a dose of a related hormone, oxytocin.  These drugs greatly enhanced the placebo effect.  These hormones play a large role in social interactions among people.  Vasopressin seems to regulate social communication and conciliatory behavior.  Oxytocin seems to be involved in experiences of empathy, trust, and social learning.  So the same chemicals that draw us together as humans and allow us to work together can also boost the placebo response altogether.

Suggestible You

March 17, 2017

“Suggestible You” is the title of a book by Erik Vance.  The subtitle is “The Curious Science of Your Brain’s Ability to Deceive, Transform, and Heal.  This book is about the placebo response and related phenomena.  One of HM’s pet peeves is the expression,”It’s just a placebo response.”  For HM, the placebo response is the most interesting effect in medicine.

Artificial intelligence pioneer Daniel Dennet has written.  “A mind is fundamentally an anticipator, an expectation-generator.”  Expectation is a system of shortcuts our brains have developed to get through the day.  Otherwise we would be stopping every few seconds to figure things out.  Consequently if what you anticipate is negative your mind will make things look (or feel) worse than they actually are.  However, if you expect the best some amazing things can happen in your body.  Somewhere between this expectation and reality lies the mind’s power to heal itself.  Erik Vance writes, “Our uncanny ability to deceive ourselves has startling implications for our health and well-being… Everyone’s door to expectation has a different key, and everyone is susceptible in a slightly different way.  But once that door is unlocked we have access to an amazing power to heal ourselves.”

Placebo comes from the Latin for “I shall please,” and traditionally refers to anything inert that has an effect on a patient.  Vance writes, “…usually lasting less than a day but sometimes longer:  a sugar pill, a saline injection, or sham surgery, often mixed with a little smoke and mirrors.  In other words, nothing.  But in the world of expectation, sometimes nothing is more powerful than something—if it’s wrapped in the right packaging.”

Vance writes that this packaging is different for everybody.  What allows a placebo to work is a topic of continuing research, the most recent of which is presented in his book.    It involves psychology, chemistry, and genetics, aided by the power of storytelling.  The manner in which the placebo is presented is important, which does not necessarily involve deception.  Placebos can be effective even when the recipient knows that it is a placebo.

Vance writes of the importance of theater or how the placebo is presented and to individual differences.  For example, depression patients respond better to yellow placebo pills than to blue ones.  Bigger ones work better than smaller ones, but only to a certain point.  Bear this in mind should you purchase placebo pills on Amazon, and there is a wide variety of placebos available on Amazon.  Fake injections work better than fake pills.  Vance goes on to note that “if you’re French, suppositories work better than either.  Take a quiet moment to ponder the significance of that.”

Placebos are a very complex topic, so a series of posts will be required, which shall follow immediately.

The Patient

May 12, 2016

The third cryptomind discussed in “The Mind Club” is the Patient.  The authors expand the concept of patient well beyond the medical context.  “Patients are perceived to have experiences and to be sensitive and susceptible to the actions of others.  Whereas agents are the thinking doers of the world, patients are the vulnerable feelers.  The word patient is likely to bring to mind the concept of pain.  The experience of pain  forces to focus on the present and how to deal with it.”

The authors wrote “Pain may have overwhelming psychological power, but the physical reality is comparatively unsubstantial.  Pain is a mental construction resulting from a handful of nerve signals.  The intensity of pain  stems only from the microscopic electrical pulses of neurons.  Moreover, pain can be triggered by nothing at all as in the case of people with neuropathic pain who live in constant agony due to a few rogue neurons.

Phantom limb pain, although quite real, indicates the fickleness.  This pain is the pain amputees feel in their amputated limb.  Neuroscientist V.S. Ramachanadran developed a special box with a mirror and two holes into which the patients place each of their arms.  The mirror faced the still-presents right hand and its reflection provided he patient with what appeared to be an intact missing limb.  Seeing this illusion significantly reduced the patient’s pain.

The placebo effect provides strong evidence on the mind’s power to influence pain.  Studies of popular drugs such as Tylenol or paracetamol for back pain, and Prozac, Effexor, or Paxil of mild depression suggest that they are no more effective than the combination of sugar pills and optimism.  Previous healthy memory blog posts have reported research in which placebos are effective even when the patients know they are placebos.

As you should know from previous healthy memory blog posts there is also a nocebo effect.  One study  found that people felt real pain after researchers put sham electrodes onto their heads  and pretended to send electric current through them.

Neuroimaging studies suggest that there is both a sensory component and an affective component to pain.  The sensory component represents actual tissue damage.  The affective component is its felt badness, its aversiveness and unpleasantness.  These components can be dissociated.  For example, morphine eliminates the aversive affect while keeping the sensory experience.    A car-accident victim treated with morphine described his experience of traumatic injury as “Pain…but not painful.”  That is the unpleasantness was dulled, but specific sensations remained intact.

In some circumstances tissue damage does not automatically translate to pain even without drugs as has been found in combat situations where soldiers carry on the battle even after having suffered grievous injuries.

Empathy is an important concept and an important skill.  Proximity is an important factor affecting empathy.   The philosopher Peter Singer formulated this thought experiment.  Imagine you are walking by a pond, wearing a new three-hundred dollar suit, when you see a drowning child.  Should you save the child even if doing so would ruin the suit?  You likely wouldn’t hesitate  to dive in.  Now consider a different scenario.  You are walking down he street after payday when a charity canvasser tells you that twenty dollars will save the life of a starving child.  Chances are you would keep your money and let the child die, even though saving the child costs a fraction of the cost of the suit.  Of course, there are factors in the comparison other than proximity.  You can actually see the drowning child, but you might have questions about the honesty of the solicitor.  But you should get the general point.

Our capacity for empathy is limited.  Although some empathy is helpful, too much can be counterproductive causing our empathy to shut down.  Psychologists Daryl Cameron and Keith Payne did an experiment illustrating the “collapse of compassion.”  They presented participants with pleas from either one or eight suffering victims.  In spite of the objectively greater total suffering of eight victims, the participants were overwhelmed by it and demonstrated less compassion.

The authors note how the Patient Mind can be mistreated as the Machine Mind.  Recent advances in neurobiology have focused attention away from human suffering and feelings and toward drugs that influence brain circuits and neurotransmitters..  Thomas Szasz has described this new psychiatry as mechanomorphic, treating patients like “defective machines” rather than fellow human beings.  The authors note “Paradoxically, physicians of the mind may fail to see their patients as members of the mind club.”

Research by Stephanie Brown of the University of Michigan has revealed that helping others can add years to your life.  She examined the mortality of older people who were the pimrary caregivers of their ill spouses.  This is a highly stressful role as caregiver must manage every aspect of their spouses’s treatment and take ultimate responsibility for the spouse’s life.  In spite of stress being linked to early death, these caregivers lived significantly longer, presumably because of increased feelings of agency.

Some time will be given to plants before ending this post.  Taking care of plants can increase longevity.  In one study,m nursing home residents given responsibility  for a houseplant outlived those who had plants that were looked after by nursing home staff.

Types of Placebos

February 25, 2016

When people think of placebos, people tend to think of pills.  Placebos can also be injections, operations, acupuncture, and so forth.  The anthropologist Moerman says that the active ingredient in placebos is meaning.   The meaning of placebo is positive.  However, there are nocebos whose meaning is negative.  Nocebos can be an effective weapon for terrorists.  Were terrorists to spray a gas over an area, people would likely get sick., even if the gas was harmless.  Or they could claim that water had been poisoned and sicknesses would likely result.  There is one theory that adverse side effects of medications are a type of nocebo.

Placebos are available for sale on the internet.  You can even find them at  And given their effectiveness, you might want to try some of these yourself.  Remember that a placebo can work even you know it is a placebo.  There are also ways of making a placebo more effective.  Size, larger being more effective, and number, more being more beneficial, are also effective.  The effects of color are more complicated with different colors being more effective for different outcomes.

This post is based on content from “Cure:  A Journey Into the Science of Mind Over Body” by Jo Marchant,

Brain Activity Underlying the Placebo Effect

August 21, 2013

Research that conducted brain imaging during placebo studies found that both the active (opiod) treatment and the placebo (saline) treatment activated the same network of brain regions. This included the brain stem, a part of the opiod system that mediates pain relief, and the rostral anterior cingulate cortex, which is rich in opiod receptors.1 It is also a part of the body’s reward system. The researcher, Petrovic, proposed that placebos, like opiods, triggered control areas such as the anterior cingulate that exerted control over the analgesic systems of the brain stem. The analgesic systems of the brain stem then released endorphins.

Another researcher, Tor D. Wager, who also used MRI found that additional brain systems were involved in the placebo effect. The researchers administered a placebo cream while giving painful shocks or painful intense heat on the forearms of the research participants. In one experiment a warning cue, a red “get ready” sign was given just before the painful stimulus was administered. The research subjects expected pain, unless the cream was applied, in which case they expected relief. The expectation of relief activated the cognitive executive center of the brain, the prefrontal cortex. Then the pain response areas of the brain declined, and the experimental participants reported relief. These results suggest that the placebo pain relief involves an expectaton signal from the prefrontal cortex that orders the midbrain to release opiods to meet the expectation of reprieve. Absent this, the full experience of pain is perceived. Further research has pinpointed specific regions of the prefrontal cortex as drivers.

Emotions are also involved in the placebo effect. Wager and his colleagues reported in 2011 that activities in regions of the brain that perform emotional appraisal, such as the insula, orbitofrontal cortex, and amygdala accompany a robust placebo effect. Wager calls this endogenous regulation. Placebos seem to give us a better perspective on our predicament. We might reevaluate our predicament so that we believe that the pain will abate and not cause persistent disability. According to Wager, during a placebo response, “our brain is likely doing a lot of the work without our real conscious input or even in spite of our conscious desires.” That is, we unconsciously engage brain mechanisms that serve to sooth.

Ironically, this self-soothing process might require us to focus on the pain rather than something else. In another study by Wager and his colleagues published in 2012, they tried to distract people away from experimentally induced pain by having them perform another task. This other task did not help relieve the pain. But when the researchers encouraged the participants to pay attention to the heat on their arm by asking them to rate its intensity, the participants experienced greater relief. This result is consistent with “acceptance” therapies or with the “relaxation response” in which people surrender to their pain to tolerate it better.

1The facts in this blog post can be found in an article, When Pretending is the Remedy, in Scientific American Mind, March/April 2013 by Trisha Gura.

The Importance of Ikigai

November 2, 2011

Ikigai is a Japanese word roughly translated as “the reason for which we wake up in the morning.” In other words, having a purpose in life. Knowing your purpose in life is important to your well being.1 Many studies have purported to show a link between some aspect of religion and better health. For example, religion has been associated with lower rates of cardiovascular disease, stroke, blood pressure, metabolic disorders, better immune functioning, improved outcomes for infections such as HIV and meningitis, and lower risk of developing cancer. Of course, it was not possible for any of these studies to be Random Controlled Trials (RCTs), where participants were randomly assigned to religious and non-religious groups. So it is possible that there is a strong element of self-selection here.

However, there are other possible reasons for these results. Religious people tend to pursue lower risk lifestyles. Churchgoers typically enjoy strong social support. And, of course, seriously ill people are less likely to attend church. However, there was recent study that tried to statistically control for these factors and concluded that “religiosity/spirituality” does have a protective effect, but only for healthy people.2 Some researchers attribute this to the placebo effect (See the Healthymemory Blog Post, “”Placebo and Nocebo Effects”). Others believe that positive emotions (See the Healthymemory Blog Post, “Optimism”) associated with “spirituality” promote beneficial physiological responses.

Still others think that what really matters is having a sense of purpose in life, whatever it might be. Presumably knowing why we are here and what is important increases our sense of control over events making them less stressful. Remember the study by Saron that was reported in the Healthymemory Blog Post, “The Benefits of Meditation.” The increase in the levels of the enzyme that repairs teleomeres correlated with an increased sense of control and an increased sense of purpose in life. The meditators were doing something they loved and provided a purpose in life.

So, it is important to have a purpose in life when you awaken in the morning. This is important throughout one’s life and is something that needs to be considered before retiring (See the Healthymemory Blog Posts, “The Second Half of Life,” and “Could the AARP Be Telling Us Not to Retire?”).

1Much of this post is based on an article, Know your purpose, by Jo Marchant in the New Scientist, 27 August 2011, p. 35.

2Psychotherapy and Psychosomatics, 78, p.81.

© Douglas Griffith and, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

Self Hypnotism

October 30, 2011

It has been said that all hypnotism is actually self hypnotism. The New Scientist published an interesting article1 on hypnotism. It describe the treatment program that Peter Whorwell has developed for irritable bowel syndrome (IBS). IBS is a serious disorder that results in some sufferers contemplating suicide. Whorwell presents a tutorial to his patients on how the gut functions. Then he has his patients effectively hypnotize themselves to use visual and tactile sensations of warmth and to imagine the bowel working normally. The United Kingdom’s National Institute for Health and Clinical Excellence has recommended hypnosis as an effective treatment for IBS. Whorwell has shown that under hypnosis some IBS patients can reduce the contractions of their bowel, something that can not normally be done under conscious control2. Their bowel linings become less sensitive to pain.

The question is why this works. Irving Kirsch of the University of Kull thinks that hypnosis taps into physiological pathways that are similar to those involved in the placebo effect (See the Healthymemory Blog Post, “Placebo and Nocebo Effects”). The medical conditions that benefit from the placebo effect and hypnotism are similar. They both involve suggestion and expectation. The disappointing part is that there are individual differences in how well people respond to hypnosis.

For those who do respond well to hypnosis, the effects can be quite impressive. A common test used in studies of pain perception is called the cold presser test. The research participant is asked to keep her hand in ice water for as long as she can stand it. This does become quite painful. The research participant gives ratings of the pain as it increases as the time in the ice water increases. Eventually, the pain becomes unbearable and the participant removes the hand. People who are effectively hypnotized can keep their hand in the bucket for a long period of time. They are told when to remove their hand to prevent organic damage. They also give accurate ratings of the pain, so although they remain aware of the painful stimulus, the pain remains bearable.

1Marchant, J. (2011). Hypnotise Yourself. New Scientist, 27 August, 35.

2Journal of Psychosomatic Research, 64, p. 621.

© Douglas Griffith and, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and with appropriate and specific direction to the original content.

Placebo and Nocebo Effects

October 16, 2011

Although you’ve probably heard of placebo effects, it is less likely that you have heard of nocebo effects. The placebo effect occurs when an inert substance, say a sugar pill or a saline injection, has curative or beneficial effects. The nocebo effect is the opposite; merely believing that a drug has harmful effects can make you suffer them. The nocebo effect can even kill.1

The expression, “It’s only a placebo effect” has almost become a cliché. But the placebo effect is one of the most amazing effects in medicine. It underscores the role that the psychology of the mind plays in healing. No respectable research in medicine can be done without a placebo control. Otherwise the effect of whatever is being tested could be attributed to a placebo effect. Placebo effects are the rule, rather than the exception, and they can be substantial.

What is more remarkable is that placebos work even when the people receiving them know that they are placebos. In one study2 the experimental group was given placebo pills with the open label placebo pills presented as “placebo pills made of an inert substance, like sugar pills, that have been shown in clinical studies to produce significant improvement in irritable bowel syndrome (IBS) through mind-body self healing processes.” The no treatment control group had the same quality of interaction with the providers, but they were not given the placebo.

The placebo group showed significantly higher scores than the control group on the IBS Global Improvement Scale, the IBS Symptom Severity Scale, and the IBS Adequate Relief Scale.

So the placebo effect cannot be simply the result of deception. Somehow, belief, a psychological variable, affects the body.

1Marchant, J. (2011). Fool Yourself. New Scientist, 27 August, 33.

2Kaptchuk, T.J., Friedlander, E., Kelley, J.M., Sanchez, M.N., Kokkotou, E., Singer, J.P., Kowalczykowski, M., Miller, F.G., Kirsch, I., Lembo, A.J. (2010). Placebos without Deception: A Randomized Controlled Trial in Irritable Bowel Syndrome. Http://